Replace string formatting with f strings. (#458)

* Replace string formatting with f strings.

* Speed up tag creation.

* Fix test patching for cold starts.

Author: purple4reina

datadog_lambda/cold_start.py

@@ -50,12 +50,16 @@ def is_new_sandbox():
 
 def get_cold_start_tag():
     """Returns the cold start tag to be used in metrics"""
-    return "cold_start:{}".format(str(is_cold_start()).lower())
+    return "cold_start:true" if _cold_start else "cold_start:false"
 
 
 def get_proactive_init_tag():
     """Returns the proactive init tag to be used in metrics"""
-    return "proactive_initialization:{}".format(str(is_proactive_init()).lower())
+    return (
+        "proactive_initialization:true"
+        if _proactive_initialization
+        else "proactive_initialization:false"
+    )
 
 
 class ImportNode(object):

datadog_lambda/handler.py

@@ -22,7 +22,7 @@ class HandlerError(Exception):
     )
 parts = path.rsplit(".", 1)
 if len(parts) != 2:
-    raise HandlerError("Value %s for DD_LAMBDA_HANDLER has invalid format." % path)
+    raise HandlerError(f"Value {path} for DD_LAMBDA_HANDLER has invalid format.")
 
 
 (mod_name, handler_name) = parts

datadog_lambda/tag_object.py

@@ -30,17 +30,17 @@ def tag_object(span, key, obj, depth=0):
         return span.set_tag(key, str(obj))
     if isinstance(obj, list):
         for k, v in enumerate(obj):
-            formatted_key = "{}.{}".format(key, k)
+            formatted_key = f"{key}.{k}"
             tag_object(span, formatted_key, v, depth)
         return
     if hasattr(obj, "items"):
         for k, v in obj.items():
-            formatted_key = "{}.{}".format(key, k)
+            formatted_key = f"{key}.{k}"
             tag_object(span, formatted_key, v, depth)
         return
     if hasattr(obj, "to_dict"):
         for k, v in obj.to_dict().items():
-            formatted_key = "{}.{}".format(key, k)
+            formatted_key = f"{key}.{k}"
             tag_object(span, formatted_key, v, depth)
         return
     try:

datadog_lambda/tags.py

@@ -1,7 +1,5 @@
 import sys
 
-from platform import python_version_tuple
-
 from datadog_lambda import __version__
 from datadog_lambda.cold_start import get_cold_start_tag
 
@@ -10,8 +8,8 @@ def _format_dd_lambda_layer_tag():
     """
     Formats the dd_lambda_layer tag, e.g., 'dd_lambda_layer:datadog-python39_1'
     """
-    runtime = "python{}{}".format(sys.version_info[0], sys.version_info[1])
-    return "dd_lambda_layer:datadog-{}_{}".format(runtime, __version__)
+    major, minor = sys.version_info[0], sys.version_info[1]
+    return f"dd_lambda_layer:datadog-python{major}{minor}_{__version__}"
 
 
 def tag_dd_lambda_layer(tags):
@@ -44,9 +42,9 @@ def parse_lambda_tags_from_arn(lambda_context):
 
     # Add the standard tags to a list
     tags = [
-        "region:{}".format(region),
-        "account_id:{}".format(account_id),
-        "functionname:{}".format(function_name),
+        f"region:{region}",
+        f"account_id:{account_id}",
+        f"functionname:{function_name}",
     ]
 
     # Check if we have a version or alias
@@ -56,12 +54,12 @@ def parse_lambda_tags_from_arn(lambda_context):
             alias = alias[1:]
         # Versions are numeric. Aliases need the executed version tag
         elif not check_if_number(alias):
-            tags.append("executedversion:{}".format(lambda_context.function_version))
+            tags.append(f"executedversion:{lambda_context.function_version}")
         # create resource tag with function name and alias/version
-        resource = "resource:{}:{}".format(function_name, alias)
+        resource = f"resource:{function_name}:{alias}"
     else:
         # Resource is only the function name otherwise
-        resource = "resource:{}".format(function_name)
+        resource = f"resource:{function_name}"
 
     tags.append(resource)
 
@@ -70,23 +68,20 @@ def parse_lambda_tags_from_arn(lambda_context):
 
 def get_runtime_tag():
     """Get the runtime tag from the current Python version"""
-    major_version, minor_version, _ = python_version_tuple()
-
-    return "runtime:python{major}.{minor}".format(
-        major=major_version, minor=minor_version
-    )
+    major, minor = sys.version_info[0], sys.version_info[1]
+    return f"runtime:python{major}.{minor}"
 
 
 def get_library_version_tag():
     """Get datadog lambda library tag"""
-    return "datadog_lambda:v{}".format(__version__)
+    return f"datadog_lambda:v{__version__}"
 
 
 def get_enhanced_metrics_tags(lambda_context):
     """Get the list of tags to apply to enhanced metrics"""
     return parse_lambda_tags_from_arn(lambda_context) + [
         get_cold_start_tag(),
-        "memorysize:{}".format(lambda_context.memory_limit_in_mb),
+        f"memorysize:{lambda_context.memory_limit_in_mb}",
         get_runtime_tag(),
         get_library_version_tag(),
     ]

datadog_lambda/tracing.py

@@ -734,7 +734,7 @@ def create_inferred_span_from_lambda_function_url_event(event, context):
     service_name = determine_service_name(service_mapping, api_id, "lambda_url", domain)
     method = request_context.get("http", {}).get("method")
     path = request_context.get("http", {}).get("path")
-    resource = "{0} {1}".format(method, path)
+    resource = f"{method} {path}"
     tags = {
         "operation_name": "aws.lambda.url",
         "http.url": domain + path,
@@ -894,7 +894,7 @@ def create_inferred_span_from_api_gateway_event(
     method = event.get("httpMethod")
     path = event.get("path")
     resource_path = _get_resource_path(event, request_context)
-    resource = "{0} {1}".format(method, resource_path)
+    resource = f"{method} {resource_path}"
     tags = {
         "operation_name": "aws.apigateway.rest",
         "http.url": domain + path,
@@ -959,7 +959,7 @@ def create_inferred_span_from_http_api_event(
     method = request_context.get("http", {}).get("method")
     path = event.get("rawPath")
     resource_path = _get_resource_path(event, request_context)
-    resource = "{0} {1}".format(method, resource_path)
+    resource = f"{method} {resource_path}"
     tags = {
         "operation_name": "aws.httpapi",
         "endpoint": path,

datadog_lambda/trigger.py

@@ -204,9 +204,7 @@ def parse_event_source_arn(source: _EventSource, event: dict, context: Any) -> s
         distribution_id = (
             event_record.get("cf", {}).get("config", {}).get("distributionId")
         )
-        return "arn:{}:cloudfront::{}:distribution/{}".format(
-            aws_arn, account_id, distribution_id
-        )
+        return f"arn:{aws_arn}:cloudfront::{account_id}:distribution/{distribution_id}"
 
     # e.g. arn:aws:lambda:<region>:<account_id>:url:<function-name>:<function-qualifier>
     if source.equals(EventTypes.LAMBDA_FUNCTION_URL):
@@ -223,9 +221,9 @@ def parse_event_source_arn(source: _EventSource, event: dict, context: Any) -> s
     # e.g. arn:aws:apigateway:us-east-1::/restapis/xyz123/stages/default
     if source.event_type == EventTypes.API_GATEWAY:
         request_context = event.get("requestContext")
-        return "arn:{}:apigateway:{}::/restapis/{}/stages/{}".format(
-            aws_arn, region, request_context.get("apiId"), request_context.get("stage")
-        )
+        api_id = request_context.get("apiId")
+        stage = request_context.get("stage")
+        return f"arn:{aws_arn}:apigateway:{region}::/restapis/{api_id}/stages/{stage}"
 
     # e.g. arn:aws:elasticloadbalancing:us-east-1:123456789012:targetgroup/lambda-xyz/123
     if source.event_type == EventTypes.ALB:
@@ -240,9 +238,7 @@ def parse_event_source_arn(source: _EventSource, event: dict, context: Any) -> s
             data = b"".join(BufferedReader(decompress_stream))
         logs = json.loads(data)
         log_group = logs.get("logGroup", "cloudwatch")
-        return "arn:{}:logs:{}:{}:log-group:{}".format(
-            aws_arn, region, account_id, log_group
-        )
+        return f"arn:{aws_arn}:logs:{region}:{account_id}:log-group:{log_group}"
 
     # e.g. arn:aws:events:us-east-1:123456789012:rule/my-schedule
     if source.event_type == EventTypes.CLOUDWATCH_EVENTS and event.get("resources"):

datadog_lambda/wrapper.py

@@ -381,9 +381,8 @@ def _after(self, event, context):
 
 
 def format_err_with_traceback(e):
-    return "Error {}. Traceback: {}".format(
-        e, traceback.format_exc().replace("\n", "\r")
-    )
+    tb = traceback.format_exc().replace("\n", "\r")
+    return f"Error {e}. Traceback: {tb}"
 
 
 datadog_lambda_wrapper = _LambdaDecorator

datadog_lambda/xray.py

@@ -41,7 +41,7 @@ def send(host_port_tuple, payload):
 def build_segment_payload(payload):
     if payload is None:
         return None
-    return '{"format": "json", "version": 1}' + "\n" + payload
+    return '{"format": "json", "version": 1}\n' + payload
 
 
 def parse_xray_header(raw_trace_id):

tests/test_tags.py

@@ -18,7 +18,7 @@ def get_mock_context(
 
 class TestMetricTags(unittest.TestCase):
     def setUp(self):
-        patcher = patch("datadog_lambda.tags.python_version_tuple")
+        patcher = patch("sys.version_info", (3, 12, 0))
         self.mock_python_version_tuple = patcher.start()
         self.addCleanup(patcher.stop)
 
@@ -65,5 +65,4 @@ def test_parse_lambda_tags_from_arn_alias(self):
         )
 
     def test_get_runtime_tag(self):
-        self.mock_python_version_tuple.return_value = ("3", "12", "0")
         self.assertEqual(get_runtime_tag(), "runtime:python3.12")

tests/test_wrapper.py

@@ -61,14 +61,13 @@ def setUp(self):
         self.mock_patch_all = patcher.start()
         self.addCleanup(patcher.stop)
 
-        patcher = patch("datadog_lambda.cold_start.is_cold_start")
-        self.mock_is_cold_start = patcher.start()
-        self.mock_is_cold_start.return_value = True
+        patcher = patch("datadog_lambda.tags.get_cold_start_tag")
+        self.mock_get_cold_start_tag = patcher.start()
+        self.mock_get_cold_start_tag.return_value = "cold_start:true"
         self.addCleanup(patcher.stop)
 
-        patcher = patch("datadog_lambda.tags.python_version_tuple")
+        patcher = patch("sys.version_info", (3, 9, 10))
         self.mock_python_version_tuple = patcher.start()
-        self.mock_python_version_tuple.return_value = ("3", "9", "10")
         self.addCleanup(patcher.stop)
 
         patcher = patch("datadog_lambda.metric.write_metric_point_to_stdout")
@@ -354,7 +353,7 @@ def lambda_handler(event, context):
 
         lambda_handler(lambda_event, get_mock_context())
 
-        self.mock_is_cold_start.return_value = False
+        self.mock_get_cold_start_tag.return_value = "cold_start:false"
 
         lambda_handler(
             lambda_event, get_mock_context(aws_request_id="second-request-id")